Basically, there are three types of NAT (Network Address Translation) which are listed below:
- Static NAT(Network Address Translation).
- Dynamic NAT(Network Address Translation).
- Port Address Translation (PAT).
Static NAT(Network Address Translation)
In a static NAT one internal network IP address to one external IP address or, in other words, we can say that one private network IP address translated to one public network IP address. All these mappings are configured by the network administrator.
Static NAT is used when a device from a private network needs to be accessible from any public network such as the internet.
Static NAT is generally used when a device in a private network need to be accessible from the outside public network.
Dynamic NAT(Network Address Translation)
Dynamic NAT is slightly different from the static NAT. In dynamic NAT, multiple private IP addresses are mapped to form a group called NAT pool.
In dynamic address translation mapping of public address to private address takes place dynamically that’s why it is named as dynamic NAT. Dynamically means router picks up the addresses from the NAT pool that is currently not assigned and it can be any address from the NAT pool of addresses. NAT translation table contains these dynamic entries as long as traffic is exchanged. After a period of inactivity, the entry time out and these addresses can be used for new translations.
Dynamic NAT is mainly used in two scenarios. The first is to give permission to protocols that create a secondary dynamic connection that reverts back to the client. Second is if there is a need for bidirectional mapping of private IP addresses to public IP addresses and don’t care about the dynamic mapping between the two.
PAT (Port Address Translation)
With Port Address Translation more than one private IP address can be translated to a single public IP address. In this port number is used to distinguish between the traffic that is which traffic belongs to which IP address, that’s why it is named as port address translation because the port is used for distinguishing the traffic. This is also a cost-effective method for establishing a connection as a large number of users in the private environment can use any public environment by using the online single global public IP address.
Port address translation is the most popular among all the NAT.
Port address translation is used when all the host uses any public network concurrently at the same time.
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